The present invention relates to the art of manufacturing structures for absorbing body exudate, more particularly to a sanitary napkin that is thin, absorbent and has a flexibility selected to provide a good comfort potential and at the same time reduce the likelihood of uncontrolled deformation in use.
In the past recent years, the sanitary protection industry has developed improved sanitary napkins that are highly absorbent and at the same time they are thin which significantly enhances their comfort potential. The conventional wisdom dictates that the comfort potential of the sanitary napkin is directly related to its flexibility, in particular the flexibility in the lateral direction. Hence, in order to improve the comfort, sanitary napkin designers have almost universally tried to create a product which is as flexible as possible. The idea behind this approach is that the flexible product will create less discomfort to the user particularly when the sanitary napkin is compressed between the thighs of the wearer.
However, sanitary napkins that are highly flexible are known to suffer from high failure rates. This can be traced to the inability of the sanitary napkin to maintain firm contact with the vaginal opening of the user. As a consequence, the menstrual fluid discharged from the vaginal opening cannot be captured immediately into the sanitary napkin and leakage that can stain the user"" undergarment may occur. This is somewhat paradoxical since a sanitary napkin that is highly flexible should, at least in theory adapt well to the anatomy of the user and maintain the condition of close contact against the skin even when the user is moving or performing another physical activity.
However, studies have demonstrated that sanitary napkins that are highly flexible when in place in the crotch portion of the user and when compressed by the user""s thighs deform laterally according to a random or uncontrolled manner. This results into the so-called xe2x80x9cbunchingxe2x80x9d problem. A sanitary napkin that bunches is compressed in a way to significantly reduce its fluid absorption area and prevent close conformation with the vaginal opening. This may explain the high incidence of failure rates observed in connection with sanitary napkins that are very flexible.
One possible manner to increase the lateral rigidity of a sanitary napkin that is taught by the prior art is to calendar the napkin between a pair of rolls. This operation stiffens the entire product by the effect of compaction. A drawback of this operation, however, is to negatively affect the absorption capacity of the sanitary napkin. The compaction effectively reduces the amount of void volume in the absorptive layers of the sanitary napkin, thus reducing its ability to store liquid.
Thus, there exists in the industry a need to provide a sanitary napkin that is thin, highly absorbent and has good comfort potential and at the same time is capable of reducing the incidence of bunching in use.
The present invention provides a sanitary napkin that has a thickness less than about 5 mm, a test capacity of more than about 8 g, a total capacity of more than about 14 g and a flexural resistance in the range from about 400 g to about 800 g. This sanitary napkin has excellent absorption characteristics and at the same time reduces the incidence of bunching. These two characteristics contribute to provide a sanitary napkin that reduces the likelihood of failures.
In a specific example, the sanitary napkin according to the invention has a cover layer, an absorbent system underneath the cover layer and a barrier layer underneath the absorbent system. The absorbent system is preferably a two-layer structure and includes a first absorbent layer and a second absorbent layer. The second absorbent layer includes a blend of cellulosic fibres and superabsorbent material. In a very specific embodiment, the second absorbent layer has been air-laid as a bottom layer of pulp, a middle layer of pulp and superabsorbent disposed in amongst the pulp and a top layer containing at least some pulp.